Dielectric relaxation and ultrafast transient absorption spectroscopy of [C6mim]+[Tf2N]−/acetonitrile mixtures

Abstract

Mixtures of the ionic liquid (IL) [C 6 influence of discrete ion pairs. Employing static dielectric constants from the DRS experiments, one finds that the lifetime of the probe in the IL mixtures is shorter than that in pure organic solvents with the same polarity parameter. This suggests an increased stabilization of the S 1 /ICT state in IL-containing mixtures, most likely due to IL-specific Coulombic interactions between the cation and the negative end of the probe's dipole. An ultrafast solvation component is observed which is ca. 0.5 ps in pure acetonitrile, and approaches the value for the pure IL (2.0 ps) already around x(IL) = 0.3. This is interpreted in terms of an efficient perturbation of the cooperative solvation response of acetonitrile by the presence of small amounts of IL and possibly also the viscosity increase when adding IL. This view is also supported by the increase of the average longitudinal relaxation time of acetonitrile upon addition of small IL amounts extracted from the DRS experiments.

The Effect of the Mixture Composition of BmimBF4-Acetonitrile on the Excited State Relaxation Dynamics of a Solar Cell Dye D149: An Ultrafast Transient Absorption Study

“…There are some previous studies where a similar red shift of absorption maxima was observed in 12'CA molecule and other carotenoids in different organic solvents, ionic liquids and even in HmimNTf2 and ACN binary mixtures and it was explained by the change of solvent polarizability defined by polarizability parameter ( ). 49,[54][55][56] Recently, Zho et al also reported similar red shift of absorption maxima of pyrene in N-butylpyridinium tetrafluoroborate-ACN binary mixture while increasing IL concentration. 57 They have discussed the effect of change of microstructure surrounding the dye and interactions between dye and ionic liquid alongside the effect of increasing viscosity as possible explanations for this behavior.…”

“…This can be explained considering the fact that, decreasing S1-S0 energy gap increases the rate of nonradiative IC process which eventually results in lower relative value. 30,49 A minimum at XIL = 0.1 also occurs in the values of emission lifetime after TA global analysis, which will be discussed later while discussing transient absorption results.…”

“…It was found a rise in the emission lifetime of the S1 state with increasing mole fraction of ionic liquid, which was explained by stabilization of S1 state due to increasing polarity of the corresponding IL-MS mixture. 49 To sum up, there are many reports focused on unraveling the excited state properties of D149 in different molecular solvents; 24,30,[32][33][34][35][49][50][51] however, to our best knowledge there is no any investigation of the excited state relaxation of D149 in IL-MS mixture. In our present work, we will fill the gap, and we are going to quantify the excited state relaxation times of D149 in the whole mixture composition range of aprotic solvent (acetonitrile), and 1-Butyl-3methylimidazolium tetrafluoroborate (BmimBF4) as well as in the neat components.…”

Dielectric properties of poly(vinylidene fluoride) composites based on Bucky gels of carbon nanotubes with ionic liquids

“…Imidazolium ion‐based ILs are the most common types and have already been industrialized in certain fields. Most studies on ILs focus on the polarity of IL or poly (IL) solutions through the dielectric behavior of these solutions in high frequency, or the solid electrolyte usually utilized in fuel cells. Computer simulations of ILs have been rapidly developed, such as simulations of molecular motion and relaxation equations .…”

Preparation and dielectric properties of poly(ε‐caprolactone) compounded with “bucky gels”‐like mixture

“…Numerous kinds of ILs are being synthesized for special use in polymer science, such as solid polymer electrolytes, [13][14][15] solar cells, [16][17][18] and plasticizers. 19,20 Most studies on ILs are focused on the polarity of IL [21][22][23][24] or poly (IL) 25,26 solutions through the dielectric behavior of these solutions, or the solid electrolyte usually utilized in fuel cells. Computer simulations of ILs have rapidly developed such as simulations of molecular motion and relaxation equations.…”